It's not easy to find a mother who would look back fondly on the time her son had cancer. But Penny (not her real name) does. Penny lives in Boston, and her son got sick when he was just 13. He struggled with the disease for several years  through the battery of tests and the horror of the diagnosis and, worst of all, through the pain that came from the treatment. For that last one, at least, there was help  Oxycontin, a time-released opioid that works for up to 12 hours. It did the job, and more.

The brain loves Oxycontin  the way the drug lights up the limbic system, with cascading effects through the ventral striatum, midbrain, amygdala, orbitofrontal cortex and prefrontal cortex, leaving pure pleasure in its wake. What the brain loves, it learns to crave. That's especially so when the alternative is the cruel pain of cancer therapy. By the time Penny's son was 17, his cancer was licked  but his taste for Oxy wasn't. When his doctor quit prescribing him the stuff, the boy found the next best  or next available  thing: heroin. Penny soon began spending her Monday nights at meetings of the support group Learn to Cope, a Boston-based organization that counsels families of addicts, particularly those hooked on opioids or heroin. (See the top 10 medical breakthroughs of 2009.)

"Penny told the group that she actually misses her son's cancer," says Joanne Peterson, the founder of Learn to Cope. "When he had that, everyone was around. When he had that, he had support."

Penny and her son are not unique. Humans have never lacked for ways to get wasted. The natural world is full of intoxicating leaves and fruits and fungi, and for centuries, science has added to the pharmacopoeia. In the past two decades, that's been especially true. As the medical community has become more attentive to acute and chronic pain, a bounty of new drugs has rolled off Big Pharma's production line.

There was fentanyl, a synthetic opioid around since the 1960s that went into wide use as a treatment for cancer pain in the 1990s. That was followed by Oxycodone, a short-acting drug for more routine pain, and after that came Oxycontin, a 12-hour formulation of the same powerful pill. Finally came hydrocodone, sold under numerous brand names, including Vicodin. Essentially the same opioid mixed with acetaminophen, hydrocodone seemed like health food compared with its chemical cousins, and it has been regulated accordingly. The government considers hydrocodone a Schedule III drug  one with a "moderate or low" risk of dependency, as opposed to Schedule II's, which carry a "severe" risk. Physicians must submit a written prescription for Schedule II drugs; for Schedule III's, they just phone the pharmacy. (Schedule I substances are drugs like heroin that are never prescribed.) For patients, that wealth of choices spelled danger. (See the most common hospital mishaps.)

"If someone is dying, addiction isn't a problem," says Dr. Jim Rathmell, chief of the division of pain medicine at Massachusetts General Hospital. "But for prescribers, the distinction between a patient who has three or four weeks to live and one who's 32 and has chronic back pain started to blur."

The result has hardly been a surprise. Since 1990, there has been a tenfold increase in prescriptions for opioids in the U.S., according to the Centers for Disease Control and Prevention (CDC). In 2007, 3.7 million people filled 21 million legal prescriptions for opioid painkillers, and 5.2 million people over the age of 12 reported using prescription painkillers nonmedically in the previous month, according to a survey by the Substance Abuse and Mental Health Services Administration (SAMHSA). From 2004 to '08, emergency-room visits for opioid misuse doubled. At the same time, the drugs have become the stuff of pop culture, gaining cachet in the process. The fictitious Dr. House and Nurse Jackie gobble them like gumdrops, as did the decidedly nonfictional Rush Limbaugh and Heath Ledger. And, like Ledger, some users don't make it out alive.

In 1990 there were barely 6,000 deaths from accidental drug poisoning in the U.S. By 2007 that number had nearly quintupled, to 27,658. In 15 states and the District of Columbia, unintentional overdoses have, for the first time in modern memory, replaced motor-vehicle incidents as the leading cause of accidental death; and in three more states it's close to a tie.